Coincident induced current switching circuits



March 23, 1965 A. H. BOBECK 3,175,062

COINCIDENT INDUCED CURRENT SWITCHING CIRCUITS Filed May 29, 1362 F IG. CURRENT 2 PULSE /5/ B SOURCE CURRENT L/ PULSE SOURCE N 22 7/23 .9/45 (SIGNAL 3 POLAR/TY POLAR/TY T 24 F/G. 3 9 CURRENT a/is cggggcAg/yl SOURCE CURRENT h soURc CURRENT SOURCE CURRENT SOURCE //v VENT'OR A. H. 5085 C A ill w,

A T TORNE V United States Patent 0 3,175,062 COINCIDENT INDUCED CURRENT SWITCHING CIRCUITS Andrew H. Boheck, Chatham, N..I., assiguor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed May 29, 1962, Ser. No. 198,544 11 Claims. (Cl. 200-87) This invention relates to electromechanical switches and, more specifically, to a plurality of switching arrangements wherein a pair of contacts are actuated by the force generated between two current-carrying conductors.

Electrical switch embodiments have been employed to accomplish a vast plurality of circuit operations ranging from elementary control and protection functions to the eminently complex interconnection and selection arrangements of which perhaps the best example to date is to the electronic telephone central otiice. The number I of different switch embodiments is also extremely large, with various arrangements being employed to open and close a pair of contacts, for example, by mechanical, magnetic and fluid means. Other prior art switches actuate a contact pair by concurrently supplying two conductors with an electrical current. The attractive or repulsive force, determined by the relative current polarities, induces motion between the two conductors thereby operating the switch contacts.

Certain applications, as for example a matrix crosspoint switch, require a switch which is capable of operating only when a predetermined combination of input signals, specifically a coincidence of input current signals, is applied thereto. Other applications, such as an oscillating switch, require a switch which operates in a relatively short period of time and which is also capable of being controlled by a combination of input sources. Prior art coincident current switches, however, have lacked this inherent capability for being responsive to combinational logic without the employment of additional, logic-generating components.

It is therefore an object of the present invention to provide an improved electromechanical switch.

More specifically, it is an object of this invention to provide a coincident current switch which actuates a pair of contacts in response to being supplied a pre-selected combination of input signals.

It is another object of the present invention to provide a switch which may be employed as a cross-point switch in a selection matrix.

A further object of the present invention is the provision of a coincident current switch which is both fastacting and highly reliable.

A still further object of the present invention is the provision of a switching arrangement which functions as a self-excited oscillator.

These and other objects of the present invention are realized in a specific illustrative embodiment thereof which includes a square loop ferromagnetic core coupled to a biasing winding, two parallel conducting rings and two switching windings. A pair of switch contacts are provided, one contact being mechanically fixed and the other joined to one of the conducting rings by an in sulating material. The conducting ring attached to the contact is pivotably mounted and spring biased to maintain the contacts in a normal position which advantageously may be either open or closed. The remaining conducting ring is fixed.

The bias winding, along with an associated bias current source, sets the core to saturation in one hysteresis remanent polarity. When it is desired to operate the switch, a current is supplied to each of the signal wind- 3,175,062 Fatented Mar. 23, 1965 ings. This energization supplies a sufficient magnetizing force to exceed the coercive force of the core thereby switching the core to its other remanent hystersis polarity.

The flux that is switched as the core changes saturation states simultaneously induces a current in each of the two conducting rings coupled thereto. The coincident ring currents establish a mutually attractive force between the rings, and the pivotably mounted conducting ring moves towards the fixed ring under the action of the attractive force, thereby operating the switch to either close or open the contacts depending upon the predetermined arrangement of the contacts.

A self-exciting switch oscillator and a switching matrix, both employing a switch substantially identical to the one described hereinabove, are also presented in detail hereinbelow.

It is thus a feature of the present invention that a coincident current switch include a ferromagnetic toroidal core, a biasing winding, two conducting rings, and two signal windings coupled to the core, and a contact pair which is in a connected or nonconnected state depending upon the realtive proximity of the conducting rings.

It is another feature of this invention that a two-dimensional switching matrix include a plurality of square loop ferromagnetic cores, a plurality of biasing windings, in one-to-one correspondence with the cores, which windings are serially connected and further connected to a bias current source, two selection windings coupled to each core, and two conducting rings coupled to each core for operating a pair of contacts.

It is still another feature of the present invention that a matrix cross-point switch include two linear cores, a conducting ring and a signal winding coupled to each core, and a pair of contacts which are operated by the relative positioning of the conducting rings.

It is yet another feature of the invention that an oscillating switch include a ferromagnetic core coupled to two conducting rings, to a biasing Winding and a signal winding, and that the switch include a con-tact pair operated by the relative proximity of the conducting rings, wherein the contact pair is serially connected to the signal winding.

A complete understanding of the present invention and of the above and other features and advantages thereof may be gained from a consideration of the following detailed description of four illustrative embodiments thereof presented hereinbelow in connection with the accompanying drawing, in which:

FIG. 1 is a combined schematic and mechanical diagram showing a specific switching arrangement which illustratively embodies the principles of the present invention;

FIG. 2 illustrates the hysteresis curve of the core included in the circuit of FIG. 1 and, further, indicates on the curve the manner in which the magnetic condition of the core is selectively controlled by the applied signals;

FIG. 3 is a diagram depicting a switching matrix which illustratively embodies the principles of the present invention;

FIG. 4 is a schematic diagram of a matrix cross-point switch embodying the principles of the present invention; and

FIG. 5 is a self-excited switching circuit which embodies the principles of the present invention.

Referring now to FIG. 1, there is shown a specific coincident current switch embodiment which employs a square loop ferromagnetic core 10, which has coupled thereto a biasing winding 21, two conducting rings 30 and 31, and a pair of switching windings 11 and 12. A pair of switch contacts 35 and 36 are provided, the contact 35 being mechanically fixed and the contact 36 joined to the conducting ring 31 by an insulating material 36a The conducting ring 30 remains in a fixed position while the ring 31 is pivotably mounted. A spring 39 biases the ring 31 in an upward position, thereby also biasing the contacts 35 and 36 in a normally closed position. A resistor 22 and a voltage source 23 are each serially connected with the biasing winding 21 and supply a biasing current thereto. The signal windings 11 and 12 are respectively connected to current pulse sources 51 and 52 which supply pulses of a nature more fully described hereinbelow.

The biasing source 23 supplies a current to the biasing winding 21 of a sufiicient magnitude to saturate the core to point N on its hysteresis curve as shown in FIG. 2, in what is termed herein the biasing remanent poiarity. The point N is primarily determined by the product of the number of turns included in the core winding 21 and the current supplied by the voltage source 23 and the resistor 22.

Each of the current pulse sources 51 and 52 supplies a current pulse which is by itself insuflicient to reverse the remanent polarity of the core. In other words, each pulse corresponds to a force less than the core coercive force plus the biasing magnetizing force. However, whenever both sources simultaneously supply energization pulses, the total magnetomotive force is then of a sufiicient magnitude to switch the core 10. In addition to the above-described pulse magnitude criterion, a further limitation may be required on either the pulse widths or the slopes of the trailing edges of the pulses, as discussed hereinafter.

To illustrate a sequence of switch operation, assume the sources 51 and S2 concurrently supply switching currents to the switching windings 11 and 12, respectively. This will switch the flux in the core 10 from the clockwise, or bias direction to the counter-clockwise, or signal polarity. When the core switches in response to this energization, coincident currents are induced in the conducting rings 30 and 31 in a counter-clockwise polarity when viewed from above.

As is well known, a mutually attractive force is generated between two conductors which carry currents in the same direction. Thus, in response to this force the pivotably mounted conducting ring 31 moves towards the fixed conducting ring 30 against the action of the tension spring 39, thereby separating the contacts 35 and 36. When the circulating currents induced in the rings 39 and 31 diminish, the contacts again move towards each other under the action of the spring 39. Additionally, when both of the signals from the sources 51 and 52 terminate, the core 10 will be reset to the bias polarity, and will return to the point N.

As is clear from the above description, the switch illustrated in FIG. 1 is inherently an AND logic switch in that the contacts are operated only if pulses are simultaneously supplied from both the sources 51 and 52. It is, of course, clear that any other logic function may be performed by simply varying the relative magnitudes of the currents supplied by the sources 51 and 52, and/ or the relative polarities of the signal windings. For example, an OR logic switch would be physically identical to that illustrated in FIG. 1 except that a single pulse from either the source 51 or the source 52 would be of sufficient amplitude to switch the core 1t Also, an Exelusive-OR logic switch would simply be an OR logic switch with the windings 11 and 12 coupled to the core 10 in respectively opposite polarities. It is apparent also that contacts 35 and 36 may advantageously be made to operate from an open condition to a closed condition by suitable modifications. The AND switch shown in FIG. 1 was selected for illustration as this is the logic performed in the selection matrix cross-point switches illustrated in the FIG. 3 arrangement.

It should be noted at this point that if the input pulses supplied by the pulse sources 51 and 52 are of a longer time duration than the period the contacts 35 and 3&5 remain open, and if the trailing edges of the input pulses are relatively steep, the switch will be actuated a second time when the core is reset to the bias point N. Hence, under the above-described conditions, the contacts 35 and as will be opened twice for each input pulse energization.

If it is desired to eliminate the second switch actuation, the input pulses may advantageously be designed to terminate while the switch is still open for the first time. This termination and the subsequent resetting action induce ring currents of an opposite polarity to the then existing circulating currents, which will either not interfere with the closing of the switch or momentarily retain the contacts in an open position depending upon the magnitude of the first circulating currents at the time the core 10 is reset, for the relative magnitudes of these opposing currents determines the magnitude of the net attractive force between the contacts at that time. Alternatively, the input current pulses can be made to diminish gradually, thereby inducing only small circulating ring currents which are insufiicient to reopen the contacts 35 and 36. Another method of eliminating a reopening of the switch is to include a diode in at least one of the conducting rings 30 or 31, which prevents a circulating current from being induced in the ring containing the diode when the core is reset to the bias remanent polarity to the point N.

Referring now to FIG. 3, there is shown a two-bytwo selection matrix employing four cross-point switches which are selected by current sources 1 and its prime y on one axis, and current sources x and its prime x on the other, or horizontal axis. Each cross-point switch is essentially identical to the switch arrangement described hereinabove and illustrated in FIG. 1 except that a difierent mechanical contact biasing arrangement, disclosed hereinafter, is employed. The respective switch components are numbered to correspond identically to the FIG. 1 switch, and subscripts have been added to identify the row and column where the element may be found. For example, the core 10 included in FIG. 3 corresponds to the core 10' in the FIG. 1 embodiment, and may be found in the first row and first column of the matrix.

Examining the cross-point switch in the first row and first column as representative of the group, note that a toroidal magnet 40 which includes a removed section, or gap, replaces the spring 39 of the FIG. 1 arrangement. The pivot of the pivotably mounted conducting ring 31 is mounted on the magnet 40 opposite to the gap contained therein, and the ring 31 extends through the gap. When the conducting ring 31 contacts either of the magnetic gap poles, it will be retained there, as it completes a low reluctance magnetic circuit bet-ween the gap pole and its pivot connection. The force of magnetic attraction, however, is made sulficiently small so that the ring 31 responds to the attractive force genenated when both the rings 36 and 31 carry coincident currents. The remaining cross-point switches are identical to the switch described above.

The switching windings 11 and 11 respectively coupled to the cores 10 and N are serially connected and further connected to the y selection source. Similarly, the remaining sources y, x and x are connected to the windings 11 and 11 12 land 12 and 12 and 12 respectively. For convenience, the biasing windings 21 21 21 and 21 are each serially connected and further serially connected to a bias current source 24. Initially, each of the conductive rings 31 through 31 associated with the cores 10 through 10 is biased in an upward condition by the magnets 40 through 40 thereby closing all the switching contacts. Assume now, that a simultaneous pulse is supplied 'by both the x and the y sources. The core 10 and the core 19 each receive only a single energization supplied to their windings 11 and 12 from the sources y and x, respectively. As the cores are set to perform AND logic, a single pulse is insufiicient to switch any of the cores, and only a small shuttle flux is switched, hence inducing only a negligible current in any of the conducting rings inductively coupled to these cores. The core induces no current in its coup-led conducting rings 30 or 31 as it receives no pulse energy at all. However, the core 10 is coupled by the windings 11 and 12 to both the y and the x pulse sources, and the two concurrent energizations supplied therefrom are sufficient to switch the hysteresis remanent polarity of the core 10 When the core 10 reverses states, a coincident current is induced in each of the conducting rings 30 and 31 creating an attractive force which moves the two rings together thereby breaking the contacts 35 and 36 associated therewith. When the ring currents diminish the switch will remain in the open position as the pivotably mounted ring 31 now completes a low reluctance path between its pivot and the south magnetic pole of the magnet 40 If it is desired that the switch return w the closed posit-ion after being momentarily opened, a spring type of arrangement as employed in FIG. 1 may alternatively be used in place of the magnets employed in the FIG. 3 embodiment. Similarly, by supplying a different combination of input signals, the switch associated with any of the other cores 10 10 or 10 may be selectively opened. An alternate matrix cross-point switch is depicted in FIG. 4, which employs two toroidal cores and 16, each composed of a linear ferromagnetic material. A fixed conducting ring 70 is coupled to the core 16 and a pivotably mounted conducting ring 71 is coupled to the core 15. The ring 71 is biased by a spring 89 in a normally up position thereby electrically joining a pair of contacts 85 and 86. The contact 85 is mechanically fixed and the contact 86 is connected to the connecting ring 71 through an insulating material 86a, thus being similar to the FIG. 1 switch. I'llustratively, a y" selection winding is shown inductively coupled to the core 15 and an x" selection winding is shown coupled to the core 16. As the cores are linear, a flux is switched in response to any variation in the applied magnetizing force which does not drive the cores into a saturation region.

To illustrate the operation of the switch shown in FIG. 4 assume both the x" and y" windings are coincidentally supplied with pulses. Each of the cores will switch flux in response to these energizations thereby inducing simultaneous currents in the rings 70 and 71 which are as a practical matter physically mounted in close proximity to one another. Ring 71 moves towards the fixed ring 70 against the action of the spring 89 thereby separating the normally closed contacts 85 and 86. When the ring currents terminate, the spring 89 will again close the cont-acts. Should either one of the signal windings be energized without the other, a current would be induced in only one of the conducting rings 71 or 70. No attractive force will be generated by a current present in only one ring and thus the normally closed condition of the contacts 85 and 86 would not be atiected. It should be noted, however, that the contacts 85 and 86 may be held apart in the FIG. 4 embodiment by supplying an alternating-current sinusoidal voltage to each of the x" and y" windings instead of the pulse voltages heretofore described. Should sinusoids be concurrently applied in phase synchronization, flux would be continuously switched, and continuous in phase currents would be induced in the conducting rings 79 and 71 thereby maintaining an attractive force which holds the contacts 85 and 86 in an open position. It should also be noted that a toroidal magnet, as shown in the FIG. 3 cross point switch embodiment, might replace the spring 89 in the FIG. 4 switch. If this were done, the switch could be electrically driven from the open to the normally closed position by supplying sinusoidal voltages to the x and y windings which are 180 out of phase.

This would induce out of phase circulating currents in the rings 61 and thereby creating a repulsive force which will reset the contacts to the normally closed position.

Another circuit arrangement employing the basic FIG. 1 switch is shown in FIG. 5, which employs the core 10, the biasing winding 21 serially connected to the biasing resistor 22, and the biasing voltage source 23. The signal winding 11, which is in the opposite polarity as the winding 21 identically as in the FIG. 1 arrangement, here has one terminal connected to the biasing source 23 with the remaining terminal connected to the contact 35. The contact 36 is electrically grounded.

To illustrate a typical sequence of operation, assume that the switch has just been closed by the action of the spring 39 and the core 10 is biased to the point N illustrated in FIG. 2. The closed switch contacts complete an electrical path from the source 23 through the wind ing 11 to ground, and a current builds up in the winding 11. The current eventually reaches a suificient magnitude to exceed the coercive force of the core 10 thereby switching the remanent flux polarity of the core, as indicated in FIG. 2, hence inducing coincident currents in the rings 30 and 31. The rings move together, in response to the attractive force generated by the currents, against the action of the spring 39 thereby opening the contacts 35 and 36 and interrupting the circuit path of the signal winding 11 and source 23. The current through this aforementioned circuit, of course, is reduced to zero as the switch contacts 35 and 36 separate, and the core is reset to the bias remanent polarity under the action of the source 23, resistor 22 and the bias winding 21. When the circulating currents in the rings 30 and 31 terminate, the contacts 35 and 36 are again closed under the action of the tension spring 39. When the contacts close a circuit is again completed through the winding 11 and current builds up starting a new cycle of operation. The switch oscillates in this manner indefinitely, and could, therefore, be advantageously employed as a pulse generator by coupling an additional winding to the core 10, or as a repeating switch by including another contact pair on the conducting ring 31.

Summarizing the basic features of the switch embodiments described herein, a magnetic core arrangement is coupled to a pair of conducting rings and a pair of contacts are respectively opened and closed depending upon the relative proximity of the rings. The ring position, in turn, is dependent upon whether or not a flux is being switched in the core, which induces coincident circulating currents in the rings, thereby generating an attractive force between them. The flux condition of the core is controlled by either one or a plurality of input signal windings, depending upon the specific logical combination of input signals to which it is desired to have the switch respond. If a square loop core is employed rather than a linear ferromagnetic core, a biasing winding is provided. Thus, the switch opens and closes in response to a fixed, Boolean logic function of input signal variables without the employment of any external logic-producing elements or circuits.

Additionally, it is to be understood that the above described arrangements are only illustrative of the application of the principles of the present invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In combination in a switch, a square loop ferromagnetic core, biasing means including a biasing winding coupled to said core for saturating said core in one hysteresis remanent polarity, a first switching Winding coupled to said core, a fixed conducting ring and a pivotably mounted conducting ring both coupled to said core, said conducting rings being adapted for relative translation therebetween, two contacts, one of said contacts being mechanically fixed and the other of said contacts being joined to said pivotably mounted conducting ring.

2. A combination as in claim 1, further including a second switching winding coupled to said core in a like polarity as said first signal winding, and two current pulse sources respectively connected to said first and said second signal windings.

3. A combination as in claim 2, further including means including a spring for biasing said contacts, and wherein said core biasing means includes a resistor and a voltage source both serially connected to said biasing winding.

4. In combination in a matrix switching arrangement, a plurality of square loop cores arranged in a matrix array, a biasing winding coupled to each of said cores, a biasing current source, said biasing windings being serially interconnected and further connected to said biasing source, two diflferent selection windings coupled to each of said cores, each of said selection windings being wound in an opposite polarity as said biasing winding, two different conducting rings coupled to each of said cores, one of each of said two rings being mechanically fixed and the other pivotably mounted, said conducting rings being adapted for relative translation therebetween, and a switch including a pair of contacts individually associated with each of said cores, one of said contacts of each pair being in a fixed position and the other of said contacts being joined to the pivotably mounted conducting ring of the associated core.

5. A combination as in claim 4, further including a plurality of toroidal magnets in one-to-one correspondence with said plurality of cores, each of said magnets including a gap, each of said pivotably mounted conductive rings being pivoted on one point of an associated one of said plurality of magnets and protruding through the gap of said magnet.

6. In combination in a matrix cross-point switch, two linear ferromagnetic cores, two signal windings, and two conducting rings, a difierent one of said windings and a different one of said rings being respectively inductively coupled to each of said cores, one of said conducting rings being mechanical fixed and the other conducting ring being pivotably mounted, said conducting rings being adapted for relative translation therebetween, and switch means including a pair of contacts, one of said contacts being fixed and the other contact being joined to said pivotably mounted conducting ring.

7. In combination in an oscillating switch, a square loop ferromagnetic core, biasing means including a biasing winding coupled to said core for saturating said core in one hysteresis remanent polarity, switching means including a switching winding coupled to said core for reversing the remanent fiux polarity of said core, fixed and pivotably mounted conducting rings coupled to said core, a switch including two contacts serially connected to said switching winding, one of said contacts being in a fixed position and the other of said contacts being fixed to said pivotably mounted conducting ring, spring means for biasing said contacts in a normally closed position,

and means responsive to said contacts being electrically connected for supplying current to said switching winding.

8. In combination in a switch, one fixed and one pivotably mounted conducting ring, a pair of contacts, means mounting one of said contacts in a fixed position, means joining the other of said contacts to said pivotably mounted conducting ring, means for biasing said switch contacts, and combinational logic responsive means for inducing coincident currents in said conducting rings for causing relative motion therebetween.

9. In combination in an oscillating switch, two conducting rings, one of said rings being fixed and the other of said rings being pivotably mounted, said conducting rings being adapted for relative translation therebetween, a switch including a pair of contacts whose separation is dependent upon the relative proximity of the conducting rings, means for biasing said pivotably mounted conducting ring, and means responsive to said contacts being electrically connected for inducing coincident currents in said conducting rings.

10. In combination in a switching matrix, a plurality of square loop ferromagnetic cores, means for biasing each of said cores to one remanent hysteresis polarity, two difiere'nt conducting rings inductively coupled to each of said cores, one of each of said two rings being mechanically fixed and the other of said rings being pivotably mounted, a plurality of switch means in one-to-one correspondence with said plurality of conducting ring pairs, said switch means being actuated in response to the relative movement of the associated ring pair, and selection means for reversing the remanent flux polarity of a selected one of said ferromagnetic cores thereby to cause relative movement of the rings mounted on said one core.

11. In combination in a switch, a pair of conducting rings, one of said conducting rings being movable, said conducting rings being adapted for relative translation therebetween, logic means including a plurality of input windings and a single toroidal core, said core being coupled to said conducting rings and said input windings for inducing circulating currents in said conducting rings in response to said windings being supplied input currents of a predetermined Boolean combination, and switch means actuated by the relative proximity of said conducting rings.

Reterences Cited by the Examiner UNITED STATES PATENTS 502,788 8/93 Thomson 3l7l68 2,793,265 5/57 Crissinger 20087 2,843,838 7/58 Abbott 340l66 2,992,306 7/61 Feiner 200-87 3,005,876 10/61 Ketchledge 174-18 3,039,055 6/22 Postal et al 317-468 OTHER REFERENCES IBM Tech. Bull., vol. 4, No. 11, April 1962, Toggle Switch by Berhman.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. IN COMBINATION IN A SWITCH, A SQUARE LOOP FERROMAGNETIC CORE, BIASING MEANS INCLUDING A BIASING WINDING COUPLED TO SAID CORE FOR SATURATING SAID CORE IN ONE HYSTERESIS REMANENT POLARITY, A FIRST SWITCHING WINDING COUPLED TO SAID CORE, A FIXED CONDUCTING RING AND A PIVOTABLY MOUNTED CONDUCTING RING BOTH COUPLED TO SAID CORE, SAID CONDUCTING RINGS BEING ADAPTED FOR RELATIVE TRANSLATION THEREBETWEEN, TWO CONTACTS, ONE OF SAID CONTACTS BEING MECHANICALLY FIXED AND THE OTHER OF SAID CONTACTS BEING JOINED TO SAID PIVOTABLY MOUNTED CONDUCTING RING. 